1. Field of the Invention
The present invention relates to a structure provided with a plurality of substrates, a manufacturing method thereof and a crystal oscillator using the structure, and more particularly, it relates to a structure provided with a plurality of substrates capable of effectively utilizing its surface area, a manufacturing method thereof and a crystal oscillator using the structure.
2. Description of the Related Art
There is sometimes a case where a circuit for performing necessary operations must be provided within a predetermined area for design reasons. If the area needed when all devices constituting such a circuit on one substrate exceeds the predetermined area, usually the substrate is divided into a plurality of substrates so that all the devices can be accommodated in the divided substrates within the predetermined area.
For example, a structure provided with a plurality of substrates is installed in an apparatus for the above-mentioned purpose. The explanation below is given by using a crystal oscillator as one example of an apparatus including a structure provided with a plurality of substrates.
A crystal oscillator is built into radio equipment, for example, as the reference source of a communication frequency. With the recent use of higher frequencies as communication frequencies, sometimes the number of components increases due to the use of multiplier circuits and the like, and there miniaturization is required.
FIG. 1 is the basic section view of a conventional crystal oscillator disclosed by the following Patent reference 1 and the like. The crystal oscillator comprises a first substrate 1a and a second substrate 1b, which are vertically disposed. On the first substrate 1a and second substrate 1b, circuit devices 2, such as a crystal oscillator, an IC, a capacitor, a resistor and the like, are installed.
The first substrate 1a has a surface-mounted external terminal 3 at each of its four corners of its base surface (back surface). A metal pin 4 is connected to the surface of each of the four corners by solder 5 as a pole and is installed on the first substrate 1a. The second substrate 1b is connected to the first substrate 1a through the metal pin 4 by solder 5 and is held above the first substrate 1a. The metal pin 4 electrically connects the respective circuit patterns of the first and second substrates 1a and 1b. Then, a metal cover, which is not shown in FIG. 1, is jointed to the first substrate 1a to cover the second substrate 1b. 
Patent reference 1: Japanese Patent Application No. H3-3506 “Temperature-compensated Oscillator”